科研之友
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摘要
Two nano-particle samples of magnetite have been prepared with average particle sizes of similar to 260 angstrom and similar to 1000 angstrom Electrical resistance of these samples has been measured in the temperature range 20-300 K and in magnetic fields up to 7.5 kOe. The two samples exhibit insulating/semi-conducting behaviour at all the temperatures. They show large magnetoresistance (MR). For the bigger particle's sample MR is 23% at 300 K and 7.5 kOe at 40 K, the value drops to similar to 4%. For the smaller particle's sample, MR is only similar to 4% at 300 K and shows slight increase to similar to 6% at 40 K. Results are suggestive of the pre-dominance of the polarized spin dependent contribution to resistivity. Observed features could be interpreted in terms of large magnetic anisotropy for surface spins of the nano-particles.
- 出版日期2011-3
